[R] sum multiple csv files

[PIKAL Petr]

Hi

see in line

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Alejandra
> Lopez-Galan
> Sent: Monday, January 15, 2018 10:29 AM
> To: r-help at r-project.org
> Subject: [R] sum multiple csv files
>
> Hi, I am pretty new to R and I would apreciatte very much your help to solve
> my problem. I have 40 csv files that have the same structure, and I want to
> merge them into a single data frame.
>
> I already have load and combined all the cvs files into a large list, and I created
> two
>
> filenames <- list.files('data',full.names=TRUE)
>
> All_data <- lapply(filenames,function(i){
>   ###read cvs files and add the row and column names to each data frame###
>   read.csv(i, header=FALSE, sep = "", col.names = col_names, row.names =
> row_names)
>  })
>
> However I would like to sum the rows of cvs files to get a single data frame
> (each cvs file has 47 rows and colunms, so the final data frame should have the
> same). I could only do it one by one data data frame, but I was wondering if

And here I am rather lost. The only possible solution (to me) is to sum all values in first row of file 1, 2, 3, ...

In that case probably the easiest way is to change list to array

aaa<-array(unlist(All_data), dim=c(47,47, 40))
result <- apply(aaa,1:2,sum)

Example:

lll <- structure(list(A = structure(list(V1 = 1:3, V2 = 4:6, V3 = 7:9,
    V4 = 10:12), .Names = c("V1", "V2", "V3", "V4"), row.names = c(NA,
-3L), class = "data.frame"), B = structure(list(V1 = 1:3, V2 = 4:6,
    V3 = 7:9, V4 = 10:12), .Names = c("V1", "V2", "V3", "V4"), row.names = c(NA,
-3L), class = "data.frame")), .Names = c("A", "B"))

> aaa<-array(unlist(lll), dim=c(3,4,2))
> aaa
, , 1

     [,1] [,2] [,3] [,4]
[1,]    1    4    7   10
[2,]    2    5    8   11
[3,]    3    6    9   12

, , 2

     [,1] [,2] [,3] [,4]
[1,]    1    4    7   10
[2,]    2    5    8   11
[3,]    3    6    9   12

> apply(aaa,1:2,sum)
     [,1] [,2] [,3] [,4]
[1,]    2    8   14   20
[2,]    4   10   16   22
[3,]    6   12   18   24

Cheers
Petr

> anyone could give an idea of how to write a function for this.
>
> Thanks,
> Alejandra
>
>       [[alternative HTML version deleted]]
>
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